In an effort to save you from this pain, I read through all the sources on ground corn that I could get my hands on (more than 20 in all) to better understand the differences between cornmeal, grits and polenta and help you shop and cook with confidence.
What is cornmeal? Technically speaking, “cornmeal” is the umbrella term for any type of “meal” made from grinding down dried corn, ranging in size from fine to coarse and coming from any variety or color of corn. Colloquially, anything labeled cornmeal found in grocery stores is likely finely ground white or yellow corn. This is the stuff you’ll use for making cornbread, to dust a pizza peel to keep the dough from sticking or as a coating for fried seafood or green tomatoes.
Grits vs. polenta. Depending on whom you ask, grits and polenta are either just the dishes made from cooking dried ground corn into a mush or also the ingredients themselves. Regarding the dishes, “Theoretically, grits and polenta are the same thing: ground corn cooked into a porridge. But, technically, polenta and grits differ in several ways, including the type of corn used to produce the ground product, as well as in the way they have traditionally been milled,” Erin Bryers Murray writes in her aptly titled book “Grits.”
Polenta dates back to Roman times in Northern Italy and was made from a range of grains and legumes before corn was introduced to the region. Since then, the dish is customarily made from eight-row flint (“otto file” in Italian) corn that has been ground via a reduction milling process that helps the corn maintain its flavor better than standard single-process milling and produces a more consistent size than stone grinding.
Grits — beloved throughout the American South and among those with connections to it — are traditionally made from dent corn. Dent and flint are both types of field corn, which is a far cry from the sweet corn you eat off the cob. The two varieties have different levels of starch firmness, which are much greater than sweet corn. “Because flint kernels are firmer than dent, cooked polenta firms up into a sturdier porridge with more defined toothiness than grits,” Byers Murray writes.
Per artisan grain producer Anson Mills, “Flints also have different basic flavor profiles when compared in similar cookery to dents. Flints possess more mineral and floral notes, dents more ‘corn’ flavor up front, followed by supporting floral and mineral notes.” Though traditionally polenta is made from flint corn, there are no regulations requiring packages labeled “polenta” to be made from it today.
I typically think of grits as white corn, because that’s what I grew up eating, but yellow grits are common as well. Historically, color preference is said to be based on whether you lived in an urban (white corn) or rural (yellow corn) area, and some heirloom producers also offer them in shades of blue and red. As for the difference between yellow and white corn: Yellow corn is said to have a more robust corn flavor, while white corn is slightly more delicate with more mineral and floral notes. However, the distinction in taste is largely negligible.
And what about hominy grits? Hominy itself is corn that has been nixtamalized, meaning that it has been treated with an alkaline solution to remove the kernel’s outer coating. This process softens the corn and is also said to aid in flavor and nutrition. While hominy can be ground to make grits, that process is said to be extinct according to Anson Mills, though other sources say this is still the case. Regardless, per Anson Mills, the use of the word hominy “is a classic Southern take on confusing terms: the popular Southern term for a dish of freshly prepared coarse grits is ‘hominy.’” So while you will still see the term on packages of grits today, it does not necessarily mean that the corn has gone through nixtamalization. (However, finely grinding true hominy produces masa harina, which is used for tortillas and tamales.)
Buying and storing. The recommended coarseness of the cornmeal you buy depends on how you intend to use it. Regular “cornmeal” in fine or medium grinds is best for baking and dredging, while medium or coarse grinds (including those labeled polenta or grits) are better suited for porridge. (Some say grits are usually coarser than polenta, others claim it’s the other way around — in my book, any medium- or coarsely ground corn will do for either.)
“The most important distinction for cornmeal is whether it’s whole grain or degerminated,” Molly Stevens writes in Fine Cooking. “Like wheat and other grains, corn kernels consist of three parts: the oil-rich and vitamin-packed germ or heart; the fibrous hull; and the starchy endosperm. Whole-grain cornmeal contains parts of all three and thus boasts a fuller, richer taste and twice the nutritional value of the other.” Whole grain varieties of cornmeal tend to be stone-ground from artisanal producers, whereas much of the commercially produced dried ground corn has been partially or fully degerminated. Stone grinding compared with modern milling techniques also preserves more of the “true corn flavor.”
While degermination may produce a less flavorful and nutritious product, it does improve convenience. “Because the germ is high in oil, whole grain cornmeal turns rancid quickly,” Stevens writes, so it has a shorter shelf life. As such, it is best stored in an airtight container in a dark, cold place (preferably the refrigerator or freezer) for maximum flavor and longevity. (The same is true even for degerminated corn, along with just about any other milled grain, including all-purpose flour.)
How to choose what to use. At the end of the day, all forms of ground corn from dried whole kernels are interchangeable, meaning you can make a porridge with the “cornmeal” you likely have in your cabinet right now or bake “grits” into cornbread (in theory). It’s mostly just a matter of preference and desired texture. (Note: Cornstarch should be treated as a completely different item because it is made from just the starchy part of the corn as opposed to the whole kernel.)